Unroll crescent rolls; press dough on bottom and sides of a 10-inch tart pan, pressing to seal perforations. Bake for 6 minutes or until lightly browned. Gently press crust down with a wooden spoon. Spread crust with mustard, and set aside.

Melt butter in a large skillet over medium-high heat. Add squash, zucchini, onion and garlic; sauté 7 minutes or until tender. Remove from heat; stir in parsley and next 4 ingredients (through pepper).

Whisk together eggs and milk in a large bowl; stir in cheese and vegetable mixture. Pour into crust. Bake for 20 to 25 minutes or until a knife inserted in center comes out clean.